In the oilfield industry, the completion of subsurface wells to produce hydrocarbons entails the insertion of casing tubulars into a wellbore traversing the subsurface formations. Specialized tools are then inserted into the casing to perforate the walls of the tubular at desired subsurface locations in order to allow the hydrocarbons in the surrounding formation to flow into the casing for collection at the surface. Once the casing is perforated, a well stimulation technique known as hydraulic fracturing is applied to create cracks in the rock formations surrounding the wellbore to create fissures or fractures through which natural gas, petroleum, and other fluids can flow more freely. In this process, a fluid is injected into the casing at high pressure to penetrate the formation via the perforations in the casing. Fracturing of a particular stage along the casing requires isolation of casing sections. In this way, the hydraulic fracture is created at the location of the perforations. In such operations, a “plug” is set in the casing to seal off the casing section to receive the high-pressure fluid. Once the fracture is initiated, a propping agent, such as sand, is added to the fluid injected into the wellbore.
After all the stages along the casing have been fractured, the series of plugs are removed so that the well can be produced via the perforations from all the stages. It is common during this drill out process to utilize a coil tubing unit or work over rig to remove the plugs placed in the well during the fracturing process. A shortcoming of plugs that are drilled out is that they leave debris in the wellbore. This debris can create problems with subsequent operations in the well, or at the surface, should it be produced. As oil and gas begin to flow into the wellbore, unwanted fluids and gasses, as well as unwanted particulates from the strata (including, sand, salts, etc.), combine with the plug debris forming a fluid mixture in the wellbore.
The fluid mixture is brought to the surface through a hydraulic process and the fluid is separated into hydrocarbon and water streams and the water is recirculated as part of the drill out process. The combined stream of Gas/Liquid Hydrocarbon/Solids/Water are generally referred to as “Flowback.” Simple frac tanks are commonly used to collect the unwanted Flowback from the wellbore. When the frac tank is full of collected fluids, sand, salts, gasses, etc., different techniques are used to process its contents. The collection, removal, and decontamination of the Flowback is an expensive process. In some cases, environmentally approved services are employed to remove the Flowback collected in the tank.
Thus, a need remains for improved techniques for separating and reclaiming Flowback arriving at the surface from a wellbore.